1. Field of the Invention
This invention generally relates to a bicycle brake lever apparatus. More specifically, the present invention relates to a technique useful when filling a hydraulic brake system for replacing the hydraulic fluid such that it is easy for residual gas bubbles during the replacement of a hydraulic fluid to retreat from a cylinder to a fluid reservoir and further prevents the backflow of the retreated gas bubbles.
2. Background Information
Disc brakes for bicycles typically include hydraulic brakes and mechanical brakes. In the case of a hydraulic brake, when filling the hydraulic brake system for the replacement of the hydraulic fluid, gas bubbles may enter into the fluid reservoir. Typically, the hydraulic brake system must be bled after the replacement of the hydraulic fluid in order to remove the gas bubbles from the system. With the gas bubbles existing in the fluid reservoir, if the bicycle should fall aside in an accident, for example, the gas bubbles will likely enter into the cylinder. Furthermore, for the fluid reservoir, it is desirable that the volume of a diaphragm in the fluid reservoir changes smoothly while ensuring the volume of the hydraulic fluid chamber within the fluid reservoir.